1. Field of the Invention
The present disclosure relates to a chassis for electronic apparatus and, more particularly, relates to that for such as a laptop personal computer (hereinafter, appropriately abbreviated as “laptop PC”), for example.
2. Description of the Related Art
In recent years, electronic apparatuses such as, for example, laptop PCs and, particularly, small-sized electronic apparatuses have been increasingly reduced in weight and thickness, for example, in order to enhance their portability and the like. As one measure therefor, the chassis which form the outer shells of such apparatuses have been increasingly reduced in thickness. On the other hand, such chassis are requested to have a required mechanical strength and rigidity and, a required electromagnetic shielding property, furthermore, requested to effectively dissipate heat generated inside the apparatuses.
Therefore, particularly in recent years, metals have been employed as materials of chassis, in many cases. As metal materials for use in such chassis, there have been light metals such as aluminum (Al) and magnesium (Mg), or alloys thereof. In general, casting or molding process has been employed for performing basic shaping.
An electronic apparatus such as a laptop PC generally includes a thin-type display section constituted by liquid crystal display panel and the like, and the chassis housing the display section in such a way as to cover its rear surface is requested to have a required mechanical strength and rigidity enough to protect the display section against external pressures, particularly, in addition to a required electromagnetic shielding property and a required heat dissipation property.
It is known that, conventionally, in a portable-type electronic apparatus, particularly, in order to ensure a required mechanical strength and rigidity while attaining thickness reduction in the apparatus, its thin-plate-shaped chassis is provided with a plurality of step portions extended substantially in parallel with each other in such a way as to form at least a bulge portion which bulges in a convex shape so that the chassis has a basic structure similar to that of an automobile bonnet, thereby ensuring that it has required rigidity while having a reduced thickness (refer to Japanese Patent Laid-open Publication No. 2003-204174, for example).
As a method for fabricating chassis having such bonnet-like basic structure, there has been widely employed a molding method which injects molten material in a molten state or a semi-molten state into predetermined molding die. In this case, a plurality of step portions is molded in such a way as extends along the direction of the flow of the molten material, in general.